The nuclear envelope (NE) encloses the eukaryotic nucleus and is involved in nuclear-cytoplasmic transport, gene regulation, DMA replication, and tethering of chromatin to the nuclear periphery. Mutations that disrupt NE function cause laminopathies, human disorders sharing the hallmark of muscular dysfunction. In agreement with the importance of NE function in muscle development and maintenance, preliminary data suggests that the recently discovered NE protein NET25 is required for differentiation of C2C12 myoblasts. The proposed work will investigate potential signaling and structural functions of NET25 at the NE pertaining to muscle cell differentiation. Molecular analysis of myogenic markers and signaling factors in differentiating C2C12 cells will specify more closely the stage at which NET25 is involved in myogenesis. Identification of NET25 binding partners by MudPIT proteomics could provide valuable information about NET25 function on the molecular level. Subcellular localization studies will test the role of NET25 in NE structure and function. Understanding the contributions of NET25 to muscle development and regeneration might provide further insight into the tissue specific defects seen in laminopathies.